You have to get the size and chew strength to suit a given dog. A dog should not be able to chew through them -- that means they are either too small or are not hard enough. There are really rock hard plastic ones that only mega-chewers can chew through. If you have one of those then it means they have to be thrown out sooner. Same with Kongs. My partner and I have a hard chewer alsatian and he only gets the hardest Kong, the black ones. Takes him ages to chew through those.

It would be dangerous to give the softer ones to a dog that chews them into chunks. They can definitely cause a fatal intestinal obstruction like any other undigestible object be it fabric, string, pieces of rug, antler, large pieces of rawhide, leather, piece of clothing etc.